인슐린의 포도당 이동 촉진 기전에 관한 연구 -세포내부 미세구조와 Cytochalasin B 결합단백질의 분포-

• 영문명: A Study on the Mechanism of Insulin Sensitivity to Glucose Transport System: Distribution of Subcellular Fractions and Cytochalasin B Binding Proteins
• 발행기관: 대한생리학회
• 저자명: 하종식(Hah, Jong-Sik)
• 간행물 정보: 『대한생리학회지』제24권 제2호, 331~344쪽, 전체 14쪽
• 주제분류: 의약학 > 의학일반
• 파일형태: PDF
• 발행일자: 1990.12.31

영문 초록

What makes glucose transport function sensitive to insulin in one cell type such as adipocyte, and insensitive in another such as liver cells is unresolved question at this time. Recently it is known that insulin stimulates glucose transport in adipocytes largely by redistributing transporter from the storage pool that is included in a low density microsomal fraction to plasma membrane. Therefore, insulin sensitivity may depend upon the relative distribution of gluscose transporters between the plasma membrane and in an intracellular storage compartment. In hepatocytes, the subcellular distribution of glucose transporter is less well documented. It is thus possible that the apparent insensitivity of the hepatocyte system could be either due to lack of the constitutively maintained, intracellular storage pool of glucose transporter or lack of insulin-mediated transporter translocation mechanism in this cell. In this study, I examined if any intracellular glucose transporter pool exists in hepatocytes and this pool is affected by insulin. The results obtained summarized as followings: 1) Distribution of subcellular fractions of hepatocyte showed that there are 24.9±1.3% of plasma membrane, 36.9±1.7% of nucleus-mitochondria enriched fraction, 23.5±1.2% of lysosomal fraction, 9.6±1.0% of high density microsomal fraction and 4.9±0.5% of low density microsomal fraction. 2) In adipocyte, there were 29.9±2.6% of plasma membrane, 19.4±1.9% of nucleus-mitochondria enriched fraction, 26.7±1.8% of high density microsomal fraction and 23.9±2.1% of low density microsomal fraction. 3) Surface labelling of sodium borohydride revealed that plasma membrane contaminated to lysosomal fraction by 26.8±2.8%, high density microsomal fraction by 8.3±1.3% and low density microsomal fraction by 1.7±0.4% respectively. 4) Cytochalasin B bound to all of subcellular fractions with a Kd of 1.0 X 10^-6M. 5) Photolabelling of cytochalasin B to subcellular fractions occurred on 45 K dalton protein band, a putative glucose transporter and D-glucose inhibited the photolabelling. 6) Insulin didn t affect on the distribution of subcellular fractions and translocation of intracellular glucose transporters of hepatocytes. 7) HEGT reconstituted into hepatocytes was largely associated with plasma membrane and very little was found in low density microsomal fraction which equals to the native glucose transporter distribution. Insulin didn t affect on the distribution of exogeneous glucose transporter in hepatocytes. From the above results it is concluded that insulin insensitivity of hepatocyte may due to lack of intracellular storage pool of glucose transporter and thus intracellular storage pool of glucose transporter is an essential feature of the insulin action.

키워드

Insulin Glucose transport Subcellular distribution Photolabelling Surface labelling Vesicle-cell fusion